In a general sense, the invention is directed to systems and methods for treating interior tissue regions of the body. More specifically, the invention is directed to systems and methods for treating dysfunction in body sphincters and adjoining tissue, e.g., in and around the lower esophageal sphincter and cardia of the stomach.
The gastrointestinal tract, also called the alimentary canal, is a long tube through which food is taken into the body and digested. The alimentary canal begins at the mouth, and includes the pharynx, esophagus, stomach, small and large intestines, and rectum. In human beings, this passage is about 30 feet (9 meters) long.
Small, ring-like muscles, called sphincters, surround portions of the alimentary canal. In a healthy person, these muscles contract or tighten in a coordinated fashion during eating and the ensuing digestive process, to temporarily close off one region of the alimentary canal from an other.
For example, a muscular ring called the lower esophageal sphincter surrounds the opening between the esophagus and the stomach. The lower esophageal sphincter (or LES) is a ring of increased thickness in the circular, smooth-muscle layer of the esophagus. Normally, the lower esophageal sphincter maintains a high-pressure zone between fifteen and thirty mm Hg above intragastric pressures inside the stomach.
When a person swallows food, muscles of the pharynx push the food into the esophagus. The muscles in the esophagus walls respond with a wavelike contraction called peristalsis. The lower esophageal sphincter relaxes before the esophagus contracts, and allows food to pass through to the stomach. After food passes into the stomach, the lower esophageal sphincter constricts to prevent the contents from regurgitating into the esophagus.
The stomach muscles churn the food and digestive juices into a mass called chyme. Then the muscles squeeze the chyme toward the pyloric (intestinal) end of the stomach by peristaltic waves, which start at the top of the stomach and move downward. The pyloric sphincter, another ringlike muscle, surrounds the duodenal opening. The pyloric sphincter keeps food in the stomach until it is a liquid. The pyloric sphincter then relaxes and lets some chyme pass into the duodenum. Dysfunction of a sphincter in the body can lead to internal damage or disease, discomfort, or otherwise adversely affect the quality of life. For example, if the lower esophageal sphincter fails to function properly, stomach acid may rise back into the esophagus. Unlike the stomach, the esophagus has no natural protection against stomach acids. When the stomach contents make contact with the esophagus, heartburn or other disease symptoms, including damage to the esophagus, can occur.
Gastrointestinal reflux disease (GERD) is a common disorder, characterized by spontaneous relaxation of the lower esophageal sphincter. It has been estimated that approximately two percent of the adult population suffers from GERD. The incidence of GERD increases markedly after the age of 40, and it is not uncommon for patients experiencing symptoms to wait years before seeking medical treatment.
GERD is both a normal physiologic phenomenon that occurs in the general population and a pathophysiologic phenomenon that can result in mild to severe symptoms.
GERD is believed to be caused by a combination of conditions that increase the presence of acid reflux in the esophagus. These conditions include transient LES relaxation, decreased LES resting tone, impaired esophageal clearance, delayed gastric emptying, decreased salivation, and impaired tissue resistance. Since the resting tone of the lower esophageal sphincter is maintained by both myogenic (muscular) and neurogenic (nerve) mechanisms, some believe that aberrant electrical signals in the lower esophageal sphincter or surrounding region of the stomach (called the cardia) can cause the sphincter to spontaneously relax.
Lifestyle factors can also cause increased risk of reflux. Smoking, large meals, fatty foods, caffeine, pregnancy, obesity, body position, drugs, hormones, and paraplegia may all exacerbate GERD. Also, hiatal hernia frequently accompanies severe GERD. The hernia may increase transient LES relaxation and delay acid clearance due to impaired esophageal emptying. Thus, hiatal hernias may contribute to prolonged acid exposure time following reflux, resulting in GERD symptoms and esophageal damage.
The excessive reflux experienced by patients with GERD overwhelms their intrinsic mucosal defense mechanisms, resulting in many symptoms. The most common symptom of GERD is heartburn. Besides the discomfort of heartburn, reflux results in symptoms of esophageal inflammation, such as odynophagia (pain on swallowing) and dysphagia (difficult swallowing). The acid reflux may also cause pulmonary symptoms such as coughing, wheezing, asthma, aspiration pneumonia, and interstitial fibrosis; oral symptoms such as tooth enamel decay, gingivitis, halitosis, and waterbrash; throat symptoms such as a soreness, laryngitis, hoarseness, and a globus sensation; and earache.
Complications of GERD include esophageal erosion, esophageal ulcer, and esophageal stricture; replacement of normal esophageal epithelium with abnormal (Barrett""s) epithelium; and pulmonary aspiration.
Treatment of GERD includes drug therapy to reduce or block stomach acid secretions. Still, daily drug therapy does not eliminate the root cause of the dysfunction.
Invasive abdominal surgical intervention has also been tried with success. One procedure, called Nissen fundoplication, entails invasive, open abdominal surgery. The surgeon wraps the gastric fundis about the lower esophagus, to, in effect, create a new xe2x80x9cvalve.xe2x80x9d Less invasive laparoscopic tehniques have also been tried to emulate Nissen fundoplication, also with success. Still, all surgical intervention entails making an incision into the abdomen and carry with it the usual risks of abdominal surgery.
The invention provides improved systems and methods for treating a tissue region at or near a sphincter. The systems and methods manipulate a support structure to form a composite lesion in the tissue region, e.g. the lower esophageal sphincter and adjoining cardia of the stomach.
One aspect of the invention provides an assembly for forming a composite lesion in a tissue region at or near a sphincter. The assembly comprises a catheter tube having a proximal end and a distal end. A support structure on the distal end carries an array of electrodes, being attachable to a source of energy capable of heating tissue when transmitted by the electrodes.
In one embodiment, the assembly further includes a handle on the proximal end for rotating the catheter tube, to position the support structure in the tissue region. The handle includes a mechanism to selectively advance the electrodes in a path to penetrate the tissue region and form, when the energy is transmitted, a first pattern of lesions. The mechanism also operates to selectively retract the electrodes, to enable rotation of the catheter tube by manipulation of the handle, to thereby rotationally shift the position the support structure in the tissue region. Advancement of the electrodes a second time forms, when the energy is transmitted, a second pattern of lesions rotationally shifted from the first pattern of lesions. Together, the first and second patterns of lesions form the composite lesion.
In one embodiment, the assembly further includes a handle on the proximal end for axially moving the catheter tube to position the support structure in the tissue region. The handle includes a mechanism to selectively advance the electrodes in a path to penetrate the tissue region and form, when the energy is transmitted, a first pattern of lesions. The mechanism also operates to selectively retract the electrodes to enable axial movement of the catheter tube by manipulation of the handle, to thereby axially shift the position the support structure in the tissue region. Advancement of the electrodes a second time forms, when the energy is transmitted, a second pattern of lesions axially shifted from the first pattern of lesions. Together, the first and second patterns of lesions form the composite lesion.
Another aspect of the invention provides an electrode carries by a support structure, which itself is carried by a catheter tube. The catheter tube also has a handle. There are different mechanisms on the handle. The first mechanism advances the electrode in a first path outward of the support structure to penetrate tissue. The second mechanism advances the electrode in a second path along the support structure to select different locations for penetrating the tissue region.
On one embodiment, the support structure includes a spine to support the electrode. In one arrangement, the first and second mechanisms advance the electrode along the first and second paths without moving the spine. In another arrangement, the second mechanism moves the spines to advance the electrodes in the second path.
Another aspect of the invention provides various methods to manipulate a support structure to form a composite lesion in a tissue region at or near a sphincter. The support structure carries an array of electrodes attachable to a source of energy capable of heating tissue when transmitted by the electrodes. The methods advance the electrodes to penetrate the tissue region and form, when the energy is transmitted, a first pattern of lesions. The methods retract the electrodes, and shift the position of the electrodes, either rotationally, or axially, or both rotationally and axially. The methods advance the electrodes a second time to form, when the energy is transmitted, a second pattern of lesions either rotationally or axially or both rotationally and axially shifted from the first pattern of lesions. The first and second patterns of lesion together comprise the composite lesion.
Features and advantages of the inventions are set forth in the following Description and Drawings, as well as in the appended claims.